#include<stdio.h>

long long z[25][25]={0};
int main()
{
	int q[21][21]={0};
	const int k1[8]={-1,-1,1,1,2,2,-2,-2};
	const int k2[8]={-2,2,2,-2,1,-1,-1,1};
	int n,m,x,y,sign,flag,a,b;
	scanf("%d %d %d %d",&n,&m,&x,&y);
	q[x][y]=1;
	z[0][0]=1;
	for(sign=0;sign<8;sign++)
	{
		a=x+k1[sign];
		b=y+k2[sign];
		if(a>=0&&b>=0) q[a][b]=1;
	}
	for(sign=0;sign<=n;sign++)
	{
		for(flag=0;flag<=m;flag++)
		{
			if(q[sign][flag]) continue;
			if(sign==0&&flag>0) z[sign][flag]=z[sign][flag-1];
			if(flag==0&&sign>0) z[sign][flag]=z[sign-1][flag];
			if(sign>0&&flag>0) z[sign][flag]=z[sign-1][flag]+z[sign][flag-1];
		}
	}
	if(q[n][m]==1) z[n][m]=0;
	printf("%lld\n",z[n][m]);
	return 0;
}
